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Joel Cohen: Top 10 key population trends on Earth with 7 billion

How can we understand a world with 7 billion people? Population expert Joel Cohen explains the top population trends on a planet with 7 billion inhabitants.

Humanity took until year 1800 to reach its first billion people. We added 1 billion people in just the past 12 years. October 31, 2011 marks a milestone in global population: 7 billion humans. That’s according to projections by the United Nations. EarthSky interviewed demographer Joel Cohen, professor of populations and head of the Laboratory of Populations at the Rockefeller University and Columbia University in New York. He explained the top 10 population trends in a world with 7 billion inhabitants.

1. One billion people are hungry, and 1 billion are obese. Cohen said this is the most important thing people should know about the population milestone of 7 billion. Too too many people on Earth today live without knowing where their next meal will come from.

A billion people are chronically hungry. That means they wake up every day hungry. They don’t get enough calories to get through the day and do a day’s work like you and me. And many of them have been hungry since they were born. And their brains aren’t fully nourished, fully developed. And they’re having a very hard time learning and coping with life’s problems.

At the other extreme there are about a billion people that are really, seriously obese. And that’s partly a matter of not getting a good food supply also — not a food supply that’s balanced for their needs. Roughly two or three billion people — we don’t know precisely — are malnourished as opposed to undernourished. That means they’re not getting the trace vitamins that they need to have a balanced diet.

In a world with 7 billion, 1 billion are hungry, 1 billion are obese. (UN)

2. Three billion people live on two dollars a day. Cohen said:

That is abject poverty. You try to live on two dollars a day for long and you’ll start losing weight pretty fast. So roughly half the world is in desperate poverty.

3. One billion people live in slums. Cohen said:

Right now, about half the world lives in cities — let’s say 3.5 billion, slightly more. And of those, a billion are living in slums without adequate sanitation, electricity, water, security, legal protection, transport, and inadequate housing conditions. When it rains, it leaks. Maybe a mud floor. So we, the world, have not provided home or food, have not reached minimum standards that we ought to be providing for people.

One billion people today live in slums. Image Credit: United Nations

4. Over 200 million woman have unmet needs for contraception. He said:

That means that they don’t want to have an additional child, and yet they’re not able to use modern means of contraception. These problems are not only abroad. We have, I would say, a very serious population problem in the United States. According to the United States Centers for Disease Control, in 2001, approximately half of the pregnancies in the United States were unintended. That means that the woman, or the couple either did not want a pregnancy at that time or did not want a pregnancy at any time. And that is a very serious problem of human well-being related to the lack of control over people’s own reproduction.

5. Today, 1.5 billion people live in rich countries. Cohen explained:

That’s Europe, Western Europe mainly, the United States and Canada, the overseas English-speaking countries of Australia and New Zealand, Japan, and some of the Asian tigers.

6. Four billion people live in middle-income countries. Said Cohen:

These are the countries that have recently emerged from poverty with fast-growing economies. And I would put China, India, Brazil, many countries in Latin America in that realm of the middle-income. And that means on the order of Chile — let’s say 5,000 dollars a year income. That’s tremendous progress when you remember how recently China and India were really in desperate poverty. And many in those countries still are.

Four billion people live in middle-income countries like China. Image Credit: weirdchina

7. Economically at the bottom are 1.5 billion people. Cohen said:

Those people are living largely in sub-Saharan Africa, but in the new world also in Haiti, and in many of the provinces of South Asia in both Pakistan, Afghanistan, India, Bangladesh. There are hundreds of millions of people in dire poverty — the bottom billion as one Oxford economist calls them. So that gives you sort of a geographical picture of where these 7 billion people are.

Seniors now outnumber toddlers.

8. Seniors now outnumber toddlers, and this trend will continue to increase. Cohen explained:

In the last decade, the world passed a very major milestone. And that is that for the first time in history, the number of people 60 years old or more exceeded the number of people 0-4 years old. Basically, for the first time, the grandparents outnumber the grandchildren. In the year 2000, there were about 10 percent of the world’s people were age 0-4, and about 10 percent were age 60+.

What we’re going into now is the era of aging. And by 2050, we anticipate that the number of people 60+ will be about 3.5 times the number of people age 0-4.

In the richer countries, like the United States and Europe, this process of aging is already pretty far advanced and will pose some serious questions and challenges for our retirement systems. In the poorer countries, which have a younger population because they’ve been growing faster — that means more children, so higher proportion of young people — aging will increase even faster than in the richer countries, which have already made a transition in part, the beginning of a transition to aging. So aging is one big thing that’s happened.

Two-thirds of people worldwide will live in cities by 2030, experts predict.

9. More than half of Earth’s inhabitants today live in cities, and two-thirds will live in cities by 2050. Cohen said:

In 2000, a little less than half of the world’s people lived in cities. Somewhere around 2007-2008, it became about 50-50. And by 2050, we expect about two-thirds of the world’s people to be living in cities. Now the increase in the number of city dwellers, between 2000 and 2050 is expected to be about three billion people, which was the total population of the Earth in 1960.

Virtually all of that additional three billion people will be added in the cities of the developing countries, not the rich countries. The rich cities will grow somewhat, but the really rapid growth will be in the poor or developing countries.

And if you do the arithmetic, 50 years between 2000 and 2050, roughly 50 weeks per year, 50 times 50 is 2500 weeks in that half century. And yet we’re going to add three billion people in the cities. Three billion is 3,000 million. It means that developing countries have to add urban infrastructure for a million people every five days from now to 2050. Now if that isn’t a building job, I don’t know what is. And hardly anybody is thinking about the design of the cities so that they can accommodate those additional three billion people in a constructive and useful way.

More than half of women today have fewer children than the number needed to replace themselves and their partner. Image Credit: United Nations

10. More than half of women today have fewer children than the number needed to replace themselves and their partner. Cohen said:

In 2003, for the first time in human history, more than half the women in the world lived in countries or provinces where the rate of reproduction was below the replacement level. That is, they were having fewer children than required to replace themselves in the next generation. This represents a tremendous change over the previous half century. The rate of growth of the world population fell by almost half, from 2.1 percent per year in 1950 to 1.1 percent per year in 2000. And we expect it to continue to decline if we continue to educate women, to provide modern contraception, and to improve the status of nutrition and education.

Bottom Line: Humanity took until year 1800 to reach its first billion people. We added 1 billion people in just the past 12 years. October 31, 2011 marks a milestone in global population: 7 billion humans. That’s according to projections by the United Nations. EarthSky interviewed demographer Joel Cohen, professor of populations and head of the Laboratory of Populations at the Rockefeller University and Columbia University in New York. He explained the top 10 population trends in a world with 7 billion inhabitants. Many continue to face issues of dire poverty. The population is aging. For the first time, more than half the world’s women live in countries or provinces where the rate of reproduction was below the replacement level.

Jorge Salazar has conducted thousands of in-depth interviews with scientists in the process of creating science content for EarthSky. He also helps host the 90-second EarthSky podcasts. Jorge has a bachelor's degree in physics from the University of Texas at Austin. He knows a lot about a lot of different things. For EarthSky, he has explored subjects as diverse as nanotechnology, ecosystem-based management, climate change, global health, international environmental treaties, astrophysics and cosmology, and environmental security. His penetrating research style, poetic writing, and ability to track down and speak with Nobel prize-winning laureates, all make him a huge asset to EarthSky.